Manufacturing method for white light source

ABSTRACT

A manufacturing method for white light source utilizes an ultraviolet light source and suitable phosphors. One of the phosphors is directly excited by the ultraviolet light source and generates a radiation with longer wavelength. Other phosphors are excited by the radiation with longer wavelength and generate radiation with much longer wavelength. The lights generated by those phosphors are mixed to form a white light.

FIELD OF THE INVENTION

[0001] The present invention relates to a manufacturing method for whitelight source, especially to a manufacturing method for high-brightnesswhite light source by an ultraviolet light source and suitable phosphorsdirectly or indirectly excited by the ultraviolet light source.

BACKGROUND OF THE INVENTION

[0002] A white light source is generally provided by mixing light sourceof different wavelength and the white light sensed by human vision isgenerally composed of light of at least two colors. For example, aconventional white light source can be realized by mixing red light,green light and blue light with suitable intensity ratio. Alternatively,the white light source can be realized by mixing yellow light and bluelight with suitable intensity ratio.

[0003] The conventional white light source generally uses at leastphosphors of different color to ensure color-rendering property.However, one of the prerequisites to provide high-efficiency white lightsource is that light from the exciting light source can be absorbed byall the phosphors. Moreover, all the phosphors have compatibleabsorption coefficients with respect to the light from the excitinglight source. Furthermore, the quantum efficiencies of the phosphorsshould be compatible to facilitate light mixing.

[0004] As can be seen above description, the phosphors should beprudently chosen to have absorption band matched with the wavelength ofthe exciting radiation. Moreover, the phosphors should have compatibleabsorption coefficients and quantum efficiency to provide white light ofhigh quality. Those requirements place a strict constrain to thematerials of the phosphors.

SUMMARY OF THE INVENTION

[0005] It is the object of the present invention to provide amanufacturing method for high-brightness white light source byultraviolet light source and suitable phosphors, wherein one phosphor isexcited by the ultraviolet light source and other phosphors are excitedby the light re-emitted from the phosphor excited by the ultravioletlight.

[0006] In one aspect of the present invention, the present inventionprovides a manufacturing method for white light source utilizing anultraviolet light source and suitable phosphors. One of the phosphors isexcited by the ultraviolet light source and generates a radiation withlonger wavelength. Other phosphors are excited by the radiation withlonger wavelength and generate radiation with much longer wavelength.The lights generated by those phosphors are mixed to form a white light.

[0007] In another aspect of the present invention, the present inventionprovides a manufacturing method for white light source utilizing anultraviolet light source and suitable phosphors. The phosphors aredirectly and indirectly excited by the ultraviolet light source and thelights generated by those phosphors are mixed to form a white light.Therefore, the ultraviolet light source and the phosphors are packagedto form a white light source with low operation current.

[0008] The various objects and advantages of the present invention willbe more readily understood from the following detailed description whenread in conjunction with the appended drawing, in which:

BRIEF DESCRIPTION OF DRAWINGS

[0009]FIG. 1 shows the excitation spectrum of the(Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ phosphor powder with reference to wavelength488 nm.

[0010]FIG. 2 shows the emission spectrum of the(Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ phosphor powder excited by a 382 nmultraviolet light.

[0011]FIG. 3 shows the color temperature variations of different BAM/YAGratios radiated by a 382 nm ultraviolet light in the CIE chromaticitydiagram.

[0012]FIG. 4 shows the excitation spectrum of the(Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂ phosphor powder with reference towavelength 600 nm.

[0013]FIG. 5 shows the emission spectrum of the((Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂ phosphor powder excited by a 470 nmultraviolet light.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention is intended to provide a manufacturingmethod for white light source utilizing an ultraviolet light source andsuitable phosphors. One of the phosphors is excited by the ultravioletlight source and generates a radiation with longer wavelength. Otherphosphors are excited by the radiation with longer wavelength andgenerate radiation with much longer wavelength. The lights generated bythose phosphors are mixed to form a white light. In the preferredembodiment of the present invention, two phosphors are used.

[0015] The ultraviolet light source can be realized by ultraviolet LED,electron beam or plasma.

[0016] The phosphor emits blue light upon excited by ultraviolet lightcan be selected from a group consisting of BaMgAl₁₀O₁₇:Eu; ZnS:Ag; and(Sr, Ca, Ba, Mg)₁₀(PO₄)₆Cl₂:Eu.

[0017] The phosphor emits yellow light upon excited by blue light can beselected from a group consisting of Y₃Al₅O₁₂:Ce, Gd; ZnS:Mn; and3Cd₃(PO₄)₂CdCl₂:Mn.

[0018] The method for preparing the phosphors used in the presentinvention are described below:

[0019] 1. Synthesizing a phosphor powder with formula BaMgAl₁₀O₁₇:Eu(denoted by BAM) such as (Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ by solid-statereaction or chemosynthesis method such as citrate sol gel orco-precipitation.

[0020] 2. Synthesizing a phosphor powder with formula Y₃Al₅O₁₂:Ce, Gd(denoted by YAG) such as (Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂ bysolid-state reaction or chemosynthesis method such as citrate sol gel orco-precipitation.

[0021] 3. Measuring the excitation spectrum of the(Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ phosphor powder with reference to wavelength488 nm. As shown in FIG. 1, the (Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ phosphorpowder can be excited by an ultraviolet light.

[0022] 4. Measuring the emission spectrum of the(Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇ phosphor powder excited by a 382 nmultraviolet light. As shown in FIG. 2, the (Ba_(0.9)Eu_(0.1))MgAl₁₀O₁₇phosphor powder emits a blue light after being excited by a 382 nmultraviolet light. The color coordinate of the blue light is determinedwith reference to 1931 CIE (commission internationale del'Eclairage)chromaticity diagram and is marked by letter “A” in FIG. 3.

[0023] 5. Measuring the excitation spectrum of the(Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂ phosphor powder with reference towavelength 600 nm. As shown in FIG. 4, the YAG phosphor powder can beexcited by a blue light with wavelength 400-490 nm.

[0024] 6. Measuring the emission spectrum of the(Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂ phosphor powder excited by a 470 nmlight. As shown in FIG. 5, the (Y_(2.3)Ce_(0.05)Gd_(0.65))Al₅O₁₂phosphor powder emits a yellow light after being excited by a bluelight. The color coordinate of the blue light is determined withreference to 1931 CIE chromaticity diagram and is marked by letter “B”in FIG. 3.

[0025] 7. Mixing the above BAM phosphor powder and YAG phosphor powderin different ratios (BAM/YAG=3.3, 5.0, 7.1 and 9.3, respectively) and a382 nm ultraviolet LED is used as exciting radiation. The colortemperature variations for different BAM/YAG ratios are shown in FIG. 3.

[0026] 8. Drawing a dashed straight line connecting points A and B inFIG. 3. As can be seen from FIG. 3, the dashed straight line passes awhite light region in the CIE chromaticity diagram. Moreover, the colortemperature variations for different BAM/YAG ratios are also locatedalong the dashed straight line.

[0027] The above BAM phosphor powder and YAG phosphor powder can bemixed in different ratio and packaged with an ultraviolet light sourceas exciting radiation, thus forming a white light source such as a whitelight LED. The package of the white light LED can be implemented in oneof the forms including lamp, SMD (surface mount device) and COB (chip onboard).

[0028] To sum up, the white light source provided by the presentinvention has peculiar advantages over prior art white light source infollowing aspects:

[0029] 1. The phosphor in the present invention can be excited by lightemitted from another phosphor. Therefore, the phosphors used in thepresent invention are not constrained to be excited by same lightsource. The applicability of phosphors is enhanced.

[0030] 2. The white light source can be formed by wide variety ofphosphors; the color-rendering property and efficiency are enhanced.

[0031] Although the present invention has been described with referenceto the preferred embodiment thereof, it will be understood that theinvention is not limited to the details thereof. Various substitutionsand modifications have suggested in the foregoing description, and otherwill occur to those of ordinary skill in the art. For example, thepresent invention can use phosphors directly or indirectly excited by anultraviolet light source and mixed in suitable ratio to provide uniformand high-brightness white light source. Therefore, all suchsubstitutions and modifications are intended to be embraced within thescope of the invention as defined in the appended claims.

I claim:
 1. A manufacturing method for white light source includingfollowing steps: providing an ultraviolet light source; directlyexciting a first phosphor by the ultraviolet light source to generate afirst emitted light; exciting a second phosphor by the first emittedlight to generate a second emitted light; mixing the first phosphor andthe second phosphor in suitable ratio to mix the first emitted light andthe second emitted light into a white light.
 2. The manufacturing methodfor white light source as in claim 1, wherein the ultraviolet lightsource is one of a LED, electronic beam and plasma.
 3. The manufacturingmethod for white light source as in claim 1, wherein the first emittedlight is a blue light and the second emitted light is a yellow light. 4.The manufacturing method for white light source as in claim 3, whereinthe first phosphor emitting blue light upon excited by ultraviolet lightis selected from a group consisting of BaMgAl₁₀O₁₇:Eu; ZnS:Ag; and (Sr,Ca, Ba, Mg)₁₀(PO₄)₆ Cl₂:Eu; and the second phosphor emitting yellowlight upon excited by blue light is selected from a group consisting ofY₃Al₅O₁₂:Ce, Gd; ZnS:Mn; and 3Cd₃(PO₄)₂CdCl₂:Mn.
 5. The manufacturingmethod for white light source as in claim 1, wherein the phosphors aremade by one of solid-state reaction and chemosynthesis method.
 6. Themanufacturing method for white light source as in claim 1, wherein thephosphors are mixed in a predetermined ratio and packaged with anultraviolet light source to form a white light source
 7. Themanufacturing method for white light source as in claim 6, wherein thewhite light source is packaged in one of the forms including lamp, SMD(surface mount device) and COB (chip on board).